Dec 18th, 2013

Author: CrossFit CDR

Energy Systems Prt II: Glycolytic

In the last blog I discussed our short-term energy system, and now I will move on to our second pathway, the glycolytic system. Glycolysis is the second-fastest way to re-synthesize ATP, and it occurs for workouts lasting several minutes and those that are moderately-powered. It would be used while performing a max effort set of push-ups or a 400 m sprint. Glycolysis can operate both anaerobically and aerobically, which means that it does not always need oxygen in order to produce ATP. In glycolysis, glucose or glycogen (stored glucose in the muscle) is broken down in a series of chemical reactions to produce pyruvate and 2 molecules of ATP. Although this pathway does not produce a lot of energy, it is very quick and will supply enough energy for your workout to go for an additional one to two minutes.

As glycolysis continues, pyruvate will go down one of two paths, it can either be turned into lactate or acetyl CoA. When the body’s oxygen supply is low, it is transformed into lactate to produce ATP. This will then lead to a build up of hydrogen ions, causing the pH to fall, and giving you that burning feeling in your muscles. If the body has a good supply of oxygen, pyruvate will turn into acetyl CoA, which will then go into the mitochondria and produce an additional 32 ATP molecules. So overall, if glycolysis is aerobic, it will produce 36 molecules of ATP.

As an athlete, it is important to know that glycolysis uses carbohydrates for fuel, meaning that you need to give your body the right carbohydrates at the right time. Good carbohydrates sources for pre-workout include oatmeal, apples, brown rice, bananas, and whole grain bread, and these should be eaten approximately 1.5-2 hours before you exercise. Immediately after exercise, so within the first 15 minutes, you should eat a high GI carbohydrate, as it will get digested quickly and replenish your glycogen stores in the muscle cells. Good examples of these include very ripe bananas, white rice, or a carbohydrate drink made with dextrose or amylopection. When your muscle glycogen stores are not replenished this could lead to muscle catabolism and decreased performance.